1. Field of the Invention
This invention relates to a linear solenoid valve apparatus having a linear solenoid valve for varying a fluid pressure corresponding to an electric signal, such as an electric current, and a valve body equipped with the linear solenoid valve. In particular, it relates to equipment for preventing a linear solenoid valve from sticking due to the presence of foreign substances at the sliding surfaces thereof.
2. Description of the Prior Art
A linear solenoid valve includes a modulator valve having a valve sleeve unit and an electromagnetic valve having a plunger and an electromagnet with a core and a coil assembly. The modulator valve includes a supply port and an output port, a spool, a spring biasing the spool, and an oil channel supplying a feedback pressure, wherein the spool is moved to a given position by balancing the force corresponding to the electric current in the electromagnet, the spring biasing force on the spool, and feedback pressure supplied to a feedback pressure chamber, to supply a regulated oil pressure from the output port.
When the linear solenoid valve is used as a hydraulic control device of a vehicle, as shown in FIG. 6, it is provided in a hole 42 in a lower portion B of a valve body.
Conventionally, a supply port 15 is formed in the upper side of valve sleeve 5 and an open portion 15c of the port is disposed to communicate with an oil supply hole 43 formed in the lower portion of the valve body "B". In the case where foreign matter is mixed in the oil, such as steel powder, in the above described linear solenoid valve apparatus, the foreign matter is apt to be introduced (1) directly to the spool 6 through an oil supply hole 42 and a supply port while supplying oil and (2) through a supply hole 43 and a supply port 15, opening upwardly, by settlement when the vehicle is stopped. Thus, there exists the danger that foreign matter will cause valve sticking by deposition on the spool 6 in the supply port 15.
When a linear solenoid valve apparatus is used for line pressure control in the hydraulic fluid control device of an automatic transmission, the linear solenoid valve apparatus operates continuously during vehicle driving. Therefore, foreign matter introduction is common. Once valve sticking has occurred, it is impossible to operate an automatic transmission smoothly.